Read: U.S. Government Assessment of Syria's Use of Chemical Weapons

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The above map, released by the White House, shows the Damascus areas of influence and areas reportedly affected by the Aug. 21 chemical attack, according to the U.S. government.

U.S. Secretary of State John Kerry, appearing to build a case for military action, said Friday that the U.S. government has "high confidence" that Syria's regime launched a chemical attack that killed 1,429 Syrians, including 426 children, in a Damascus suburb.

He spoke of Syrian President Bashar al-Assad as a "thug and a murderer" and described the attack on Syrian civilians as a "crime against humanity."

Three days before the Aug. 21 attack, Syrian regime personnel were "on the ground" making preparations for the weapons' use, Kerry said. The regime personnel were told to wear gas masks and the rockets came from regime-controlled areas, he said.

Here is the four-page document released by the United States on Friday outlining the case that Syria used chemical weapons: